Does a Low Protein Diet Slow Aging, Protect Against Cancer and Inhibit Prostate Cancer Growth?

Longer Life Foundation Longevity Research Program:
John O Holloszy M.D., Director
Luigi Fontana M.D. Ph.D., Associate Director


Project Overview:
Many studies on mice and rats have shown that calorie restriction (CR) slows aging. There is currently no evidence that CR slows aging in humans. The goal of this study is to obtain evidence regarding whether members of the Caloric Restriction Society (CRS), who have been practicing CR for an average of 11 years, are physiologically younger than their chronological age.

A number of cardiovascular physiological functions and anatomical properties deteriorate linerally between the ages of 30 and 70, with an accelerated decline after age 70. The approach we are using is to measure some of these functions in individuals in the 28 to 80 year age range who are practicing long-term CR and in two age-matched comparison groups.

One comparison group consists of healthy, normal weight individuals eating usual U.S. diets. The second group are healthy, lean endurance athletes. This study is made possible by the availability of highly motivated individuals who are practicing long-term CR with optimal nutrition and are interested in participating in a study on their rate of aging. These individuals, who are members of CRS, believe that CR will enable them to live far longer in good health than they would have on their previous diets. Fifty strictly observant CR practitioners have committed themselves to come to our laboratory for testing. These CR individuals reduced their food intake by about 25 to 30% and have now been stable at their lower body weight for years.

Our general approach is to relate the various cardiovascular function measurements that we are making to age with the goal of determining whether the slope of the line relating the function measurement to age (i.e. the rate of deterioration) is less steep in the CR group than in the comparison groups.

Our research has significance relative to the current epidemic of overeating leading to obesity, type 2 diabetes and other health problems. While the majority of middle-aged and older people in North America are overweight or obese, there is a large subgroup interested in eating healthy diets, as evidenced by the popularity of the Whole Food Supermarkets, the increasing sales of “organic” produce, and the growing number of vegetarians.

If our research provides convincing evidence that CR slows aging, this finding will receive considerable publicity and likely encourage the trend toward healthier eating habits. Such evidence could also be used in campaigns to reduce intake of “empty calories.” Although not many people would want, or be able, to restrict food intake as severely s the CRS members, such campaigns should be based on the understanding that CR is not an all or none proposition, and that milder degrees of CR are also beneficial. If this study provides evidence that CR slows aging in humans, this finding would also validate the search for CR mimetics and provide significant further impetus to this area of research.